The invention relates to a thermally and hydrothermally stable synthetic material having a high void volume attributable to tortuous mesopore-sized channels having a mean diameter between about 15 xc3x85 and about 100 xc3x85 and a narrow size distribution of less than or equal to about 30 xc3x85, and a process for preparing same, so as to provide an excellent starting material for incorporation of active materials and the like.
Amorphous silica-aluminas are commercially used catalysts in many processes due to their acidity. The two most common methods for preparing amorphous silica-alumina are the controlled deposition of an alumina salt on a silica surface, and the co-precipitation of silica and alumina species from solution. In the first method, the silica surface is prepared from a silica gel, and alumina salt is hydrolyzed and precipitated by addition of aqueous ammonia.
The first method, controlled deposition of alumina on silica gel, leads to the generation of tetrahedrally coordinated aluminum, due to the controlled incorporation of the hydrolyzed aluminum atoms into the silica structure. In practice, however, this method is not desirable because the porosity of the silica gel collapses upon thermal treatment, for example during calcination, thereby making the aluminum atoms inaccessible to hydrocarbon molecules or other materials to be treated, thereby diminishing the practical value of such composition for commercial processes.
The second method, co-precipitation, leads undesirably to a large amount of octahedrally coordinated aluminum.
It is therefore evident that the need remains for a synthetic material wherein alumina and other active materials can be incorporated or deposited in tetrahedrally coordinated position with silica and wherein the composition maintains its porous structure without collapsing during calcination and/or other high temperature processes.
It is therefore the primary object of the present invention to provide a material on which active materials can be deposited and dispersed which material is thermally and hydrothermally stable.
It is a further object of the present invention to provide a method for preparing such a material.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the invention, the foregoing objects and advantages are readily attained.
According to the invention, a composition of matter is provided which comprises an inorganic porous material having wall portions defining mesopore-sized channels having a mean diameter of between about 15 xc3x85 and about 100 xc3x85 and a narrow diameter distribution of less than or equal to about 30 xc3x85, said material having a void volume from said mesopore-sized channels of at least about 0.1 cc/g and a surface area of at least about 500 m2/g and having a number of hydroxyl groups of at least about 1.5 mmol of hydroxyl groups per gram of material, and exhibiting thermal and hydrothermal stability at temperatures up to about 500xc2x0 C.
In further accordance with the present invention, a process is provided for preparing an inorganic porous material in accordance with the present invention, which process comprising the steps of forming a solution of a hydrolyzable inorganic compound with a non-ionic tensoactive organic molecule; inducing growth and condensation of a solid composition comprising an inorganic composition in intimate contact with said organic molecule; and extracting said organic molecule with a solvent so as to provide a porous solid composition having a porous structure and having a number of hydroxyl groups of at least about 1.5 mmol of hydroxyl groups per gram of material, wherein said material maintains said porous structure upon thermal and hydrothermal treatments at temperatures of up to about 500xc2x0 C.
In accordance with the present invention, solvent extraction and calcination can be used, if desired, to control the number of hydroxyl groups present in the resulting inorganic porous material.
Further, an active material such as an active metal or non-metal, absorbent or adsorbent agents, and the like, may readily be deposited directly upon the inorganic porous material to provide a wide variety of catalysts useful in various applications in accordance with the present invention.